VAT on printed matter and mailing packages

Question

We are a medium-sized print production company. Many of our clients are partially exempt and have benefited from the zero rating of the mail packs we produce under a single source solution; typically this covers the design and printing of the mail packs sourcing address lists and arranging delivery. We understand that HMRC has always viewed these services as standard rated but has now issued updated public notices to reflect this. If we have applied the zero rating based on previous guidance can we assume that there will be no assessments for supplies made before 31 July 2015? Are there any circumstances in which mail packs can continue...